The invention relates to an internal combustion engine with a level plate that is arranged between a cylinder head and a cylinder, is adjacent to a combustion chamber, and is provided with at least one opening for at least one inlet valve and/or one outlet valve and/or at least one injection equipment or the like, the plate bordering on a level cylinder head bottom.
U.S. Pat. No. 4,774,912 A discloses a cylinder head for an internal combustion engine consisting of an upper part of a rigid structure that is provided with the cooling water passages and is closed by a bottom plate bordering on the water passages. The two parts of the cylinder head are joined to form a single common structure. As compared to the upper part, which is of a rigid structure, the bottom plate is made from a metal of higher high-temperature strength and lower thermal conductivity. Higher cylinder pressures may thus be realized. However, the water passages, which directly abut on the bottom plate, require the upper part to be constructed separately and sealing measures for the coolant to be carried out, which increases the cost of production.
The German Patent No. 33 07 115 A1 describes a cylinder head for an internal combustion engine, whose face opposing the combustion chamber is covered by a plate that is provided with openings for valves, spark plugs or injection nozzles. This plate is intended to insulate the cylinder head on the side of the combustion chamber. The circular plate is thereby shrunk in a collar configured in the cylinder head. This presents the disadvantage that the cylinder head bottom must be processed separately and that the shrinking procedure requires additional stages, which again substantially increases the cost of production. Furthermore, the cylinder head bottom is weakened by stress concentration. Similar plates have been described in the publications CH 389 990 A, DE 35 23 131 C1 and DE 30 39 718 A1.
The British Patent GB 111 095 A1 discloses an internal combustion engine with a bottom plate that borders on a level cylinder head bottom. The valve seat is provided in the bottom plate.
It is the object of the present invention to achieve in the easiest possible way that, in an internal combustion engine of the type mentioned herein above, less heat be introduced into the cylinder head.
This is achieved in accordance with the invention in that the diameter of the opening is larger than the valve seat for the inlet valve and/or for the outlet valve and that the valve seat for the inlet valve and/or for the outlet valve is formed by the cylinder head or by a valve seat ring that is solidly connected thereto. Accordingly, the function of the valve seat is performed by the cylinder head in a conventional manner. As a result thereof, the plate can be very simple in construction. The level plate is thereby flush with a level connecting face of the cylinder head bottom. The cylinder head bottom needs not be provided with collar-like cavities in order to insert the plate. Accordingly, the cylinder head bottom is of a closed and level realization except for the openings for the inlet valves, the outlet valves, the injection equipments, the blowby of water and/or the cylinder head studs. As a result thereof, a standard cylinder head may be used without any constructional change or additional stages in processing. Existing standard cylinder heads can be readily retrofit using the bottom plate. Furthermore and in spite of the protruding valves, a piston without pocket, i.e., with a crown that is level too, may be utilized. For reasons of stability this is to be preferred when ignition pressures and thermal stress are high.
In a variant in accordance with the present invention there is provided that the diameter of the plate corresponds at the utmost to the bore diameter of the cylinder. In this event, the plate has a circular outline and is preferably fastened to the cylinder head by means of fastening screws. Alternatively or in addition thereto, a swivel nut may fasten the plate in a location bore for the injector.
In a particularly preferred variant of the invention there is provided that the plate extends completely beyond the cylinder and is pressed against the cylinder block and/or a cylinder liner arranged in said cylinder block by the cylinder head. A separate cylinder head gasket may be dispensed with when the plate constitutes a sealant between cylinder head and cylinder block and forms the sealing faces toward the cylinder housing and/or the cylinder liner.
The plate may thereby extend along the entire length and/or width of the cylinder head. The cylinder head may be designed as a single cylinder head or as a multi-cylinder head. It is of particular advantage when the plate is provided with at least one port for the blowby of water between cylinder housing and cylinder head. As a result thereof, no separate sealants are needed in the region of the blowby of water between cylinder housing and cylinder head either. Advantageously, the plate is also provided with passage holes enabling passage of cylinder head studs that press the plate via the cylinder head against the cylinder housing or the cylinder liner.
In a particularly preferred variant of the invention, the plate is provided with a bezel on the side of the combustion chamber, around at least one opening for an inlet or an outlet valve. The bezels can have an individual geometry that is favourable to the flow. This is particularly made possible when the bezel has at least two regions with differential angles of the bezel that are defined between said bezel and a parallel to the axis of the cylinder, the change in the angle of the bezel between the regions being preferably designed to be continuous, the valve seat rings being, as already described, arranged in the cylinder head bottom in the same way as conventional cylinder heads. Since the bezels of the cylinder head bottom for the inlet or outlet valves are not arranged in the cylinder head bottom but in the plate, the effective height of the valve seat ring may be reduced, which has a favourable effect on guiding the coolant in the water cooling jacket of the cylinder head.
To effectively reduce the introduction of heat into the cylinder head bottom, it is particularly advantageous to have the plate made from a highly creep-resistant alloy or from ceramics. However, it is also possible to make the plate from an austenitic or martensitic stainless steel or from cast steel.